Storage media known as memory cards have been widely used in recent years. These memory cards are configured of flash memory or other nonvolatile memory that has been packaged in a card shape. The popularity of these memory cards has spread rapidly in such applications as storage media for digital cameras, portable music players, and other digital devices. A variety of memory cards with no common standardized specifications have appeared on the market, including CompactFlash (registered trademark; hereinafter also abbreviated as “CF”), SmartMedia (registered trademark; hereinafter also abbreviated as “SM”), Memory Stick (registered trademark; hereinafter also abbreviated as “MS”), and Secure Digital Cards (registered trademark; hereinafter also abbreviated as “SD”).
Memory card readers/writers (hereinafter abbreviated as “readers/writers”), which are capable of reading from and writing to memory cards, are connected to the personal computer or the like, enabling the personal computer to access the memory cards. With this construction, data communications can be performed between the personal computer and the memory cards. The types of readers/writers include a single-slot reader/writer equipped with one slot for inserting a memory card, and a multi-slot reader/writer provided with a plurality of slots so that data can be accessed from a plurality of memory cards. These readers/writers are described in U.S. Patent Application Publication No. 2005/0023339 (corresponding to Japanese Patent Application Publications Nos. 2005-18645 and 2005-107875).
As the volume of data transfers has increased dramatically with the popularity of multimedia, serial communications has become the common format for communications between the readers/writers described above and a personal computer. However, many devices continue to use the system employed in parallel communication peripheral devices for arbitration/access control from the perspective of facilitating the control of data accesses for a plurality of storage medium. A typical example is a system designed to implement data communications between a personal computer and reader/writer based on a protocol defined by the SCSI standard (also referred to as the SCSI protocol below). The SCSI standard was established by the American National Standard Institute (ANSI) and has been widely adopted throughout the world as a communication protocol because this protocol can enhance the versatility of personal computers and readers/writers. In the following description, “SCSI standard” will primarily refer to SCSI-2.
According to SCSI protocol, the personal computer, which is the host device, functions as the initiator for starting communication events, while the peripheral device functions as the target of communications from the host device. The personal computer issues a sequence of commands to the peripheral device for executing a communication event, and upon receiving these commands the peripheral device sequentially executes processes corresponding to the commands (such as data reading, writing, deleting, and various incidental processes) and issues response information corresponding to the execution results to the host device. Hence, the commands for executing the communication event are restricted to one direction from the host device to the peripheral device.